1. Field of Invention
The invention is related to an ink jet printing apparatus and an adjustable driving method for the ink jet printing apparatus.
2. Description of Related Art
There has been an ink jetting device having an ink jet head formed with piezoelectric ceramics as an ink jetting device used for an ink jet printer. A plurality of ink channels spaced by the piezoelectric ceramics are provided in this type of ink jet head. An ink cartridge storing ink is connected to one end of each ink channel and the ink stored in the ink cartridge is supplied to the ink channel. A nozzle for ejecting the ink in the ink channel is provided to the other end of each ink channel.
When ink droplets are ejected from the ink channel, a voltage corresponding to a driving signal is applied to the piezoelectric ceramics to deform the piezoelectric ceramics. The capacity of the ink channel is changed by the deformation. When the capacity of the ink channel is decreased, the ink in the ink channel is ejected from the nozzle, and when the capacity of the ink channel is increased, the ink in the ink cartridge is introduced to the ink channel. The ink ejected from the nozzle is printed on the paper as a character or a figure.
Although the ink jet head is made with very high accuracy, it is impossible to completely prevent variation in the size of the ink channel or the nozzle for each ink jet head. Therefore, the size of the ink channel or the nozzle is different for each ink jet head. If the size of the ink channel is different for each ink jet head, the deformation amount of the ink channel becomes different when the same driving voltage is applied to the piezoelectric ceramics. If the deformation amount of the ink channel is changed, the voltage applied to the ink in the ink channel at the time of change of the capacity of the ink channel is changed, therefore, the ejecting speed of the ink is changed. Further, if the size of the nozzle is different, the amount of the ejected ink or the ejecting speed is changed.
If the ejecting speed is changed as described above, the following problem is caused. When the ink jet head moves along the paper reciprocately to eject ink droplets, the adhering position of the ink droplet on the paper becomes different when the ink jet head moves forward and when the ink jet head moves back. Especially, in a multi-color ink jet printer provided with a plurality of ink jet heads corresponding to each color, the adhering position of the ink droplets of each color becomes different and therefore, printing with high quality cannot be performed.
Thus, the manufacturing error of all ink jet heads must be within a range of the predetermined tolerance to maintain predetermined printing quality in any ink jet head, and it has been necessary to manage the size of the ink channel or nozzle with strict tolerance in the manufacturing process of the ink jet head.